Copper base alloys



Patented Mar. 17, 1936 UNITED STATES PATENT OFFICE COPPER BASE ALLOYS NoDrawing. Application October 13, 1934, Serial No. 748,194

17 Claims.

This invention relates to a copper base alloy composed mainly of copper,cadmium, nickel and aluminum.

It is an object of the invention to provide a copper base alloy which isnot much harder and has somewhat greater strength than copper withworkability, toughness, resistance to intercrystalline attack orcorrosion and other desirable characteristics and physical properties,but which, after fabrication, may be hardened and strengthenedconsiderably, if desired, by a suitable low temperature heat treatment.

The foregoing and other objects will appear from the followingdescription and appended claims.

We have discovered that there is a range of alloyscontaining copper,cadmium. nickel and aluminum in the proportions hereinafter mentionedwhich have desirable characteristics and physical properties not presentin other commercial copper base alloys. One very important feature ofthese new alloys is the great increase in hardness that may be obtainedby heat treatment at low temperatures. The new alloys are hardenable attemperatures from 300 C. to 550 C., and are annealed or softened attemperatures somewhat above 700 C. For example, an alloy containingapproximately 93% copper, 1% cadmium, 5% nickel and 1% aluminum that hadbeen cold rolled from 0.500" gauge to 0.100" gauge has a Rockwell Ghardness value of 53 (G scale 5" ball, 150 kg. load). After being heattreated in an electric muiile furnace for two hours at 500 C., thehardness value of this same sample is increased to 81. After the saidalloy has been annealed at 850 C. for 2 hours and quenched in coldwater, the G hardness value is minus 34, which, after the specimen isheat treated for 2 hours at 525 C., is raised to G 60. When consideredfrom a numerical standpoint, this Rockwell G hardness range of minus 34to plus 81 (115 numbers) is exceptionally wide for a non-ferrous alloy.

The tensile strength ranges from about 39,900 lbs. per sq. in. to atleast 91,600 lbs. per sq. in. for the said alloy. Worthy of note is thatwith 91,000 lbs. tensile strength there is obtained an elongation of 10%in 2" in this hard rolled sample after low temperature precipitationheat treatment. This indicates that our new alloy has not beenembrittled by the heat treating operation, which condition is found insome precipitation hardening alloys.

The great increase in hardness and tensile strength is brought about byrapidly cooling the ened by low temperature heat treatment. Be-

cause the alloy is not susceptible to softening at temperatures up toabout 525 C., it is suitable for condenser tubes, parts for internalcombustion engines, bearings and other uses subject to operatingtemperatures below 525 C. In other words it has thecharacteristic' ofhigh resistance to creep (gradual elongation) under stress even atelevated temperatures, for instance up to about 525 C.

These new alloys that have been precipitation hardened and/or workhardened by rolling and/or drawing can be softened by-annealing at about800 C. and quenching in cold water. The annealed or work hardened metal,whether in the form of sheet, rod, tube, et al., can be readilyfabricated into the'finished product and then hardened by heat treatmentat a low temperature. This (a type of heat treatable alloy) isespecially suitable for such articles as nuts, bolts, nipples, valves,fittings, wire screens, coins, bushings, bellows, containers, pipes,jewelry, etc.

Another very important feature of these new alloys is theexcellentresist-ance which they offer to attack by corrosion. The newalloys are almost impervious to intercrystalline attack or corrosionwhen exposed to steam and hot water under pressures as high as 140 lbs.per sq. in. for long periods of time. This strong resistance tocorrosion was found in the alloys even when stressed up to percent ofthe ultimate tensile strength in a steam chamber with the steam pressuremaintained at about 130 lbs. per sq. inch. They also have excellentresistance to corrosion in air at temperatures above normal.

After annealing or heat treating these new alloys, the presence ofathin, brick red film was observed on the surface of the wire. This filmor tarnish was also noted -on annealed wire which had been pickled indilute sulphuric acid (1 to 10) thoroughly rinsed in water and dried inan oven at about C. This filmappears to afford some protection againstintercrystalline attack or corrosion.

The new alloys possess valuable corrosion resistance properties that areespecially suitable for use in steam expansion joints, condenser tubes,flexible metal hose, welds, valves, tanks and the like, and are alsovaluable for general structural and fabricating purposes.

Several of the alloys made in accordance with the. present invention maybe hot rolled, forged, extruded, pressed, stamped, etc. at a red heat,and therefore can be fabricated into various articles at moderateexpense. Many of these new alloys may also be cold rolled or drawn inaccordance with the regular practice for copper base alloys. A few ofthe alloys in this range'will cold work satisfactorily but cannot besuccessfully hot worked and vice versa; some of the alloys may be hotworked successfully but will not cold work satisfactorily. Thecomposition 'range of the alloys embodying the aforementioned advantagesis as follows:

In order to obtain alloys which will hot and (or) cold worksatisfactorily, it is necessary to change the composition within theabove mentioned range. As the nickel and (or) aluminum content isincreased, the cadmium content is decreased. For example, for an alloycontaining 5 per cent nickel and 1 percent aluminum, the maximum amountof cadmium permissible for hot rolling is about 1.5 percent. An alloywith approximately 15 percent nickel and 1 percent aluminum shouldpreferably not contain more than about of one percent cadmium. An alloycontaining approximately 5 percent nickel and 2 percent aluminum shouldpreferably not have more than about 1 percent cadmium present. It isnecessary to limit the cadmium content to the degree stated in orderthat the alloy may be capable of extensive hot and (or) cold working.The relative nickel and aluminum content with the maximum amount ofcadmium advisable in the hot workable alloys are given in the followingtable:

Cadmium Alumi- Copper (maximum) eke! num It is to be noted that althoughdefinite percentages have been given in these tables they areillustrative only and that intermediate percentages of Ni, Al and Cd maybe used as desired,

' and in such intermediate alloys the advisable maximum Cd content willcorrespondingly vary. The maximum hardness in the above series ofalloys, most of which are heat treatable, was obtained where the nickelcontent exceeded the Per cent Cadmium .01 to 1.5 Aluminum .5 to 4 Nickel3 to 30 Copper Balance An alloy which we have found to have verydesirable properties particularly for use in condenser tubes or in thepresence of steam and which is also adapted for various articles assheets, rods, wire tubes, forgings etc. comprises approximately 1%cadmium, 5% nickel, 1 to 5% aluminum and balance copper. This alloy withan aluminum content up to approximately 2% can be both hot and coldworked, and from approximately 2 to 5% aluminum it is capable of coldworking.

Alloys comprising approximately 78.5% copper, 0.5% cadmium, 20% nickeland 1% aluminum; and approximately 83.25% copper, 0.75% cadmium, 15%rickel and 1% aluminum, have been found to be very desirable for usewhere exposed to steam or other corrosive influences, and also forarticles which can be fashioned by working hot or cold and subsequentlyhardened by heat treatment, and particularly where a white color isdesirable.

The beneficial effect of cadmium plus nickel plus aluminum on copper isvery marked even when each of these three elements is in small amounts,such as from,0.01% to 0.10%, particularly as to increase in hardness,resistance to corrosion and intergranular disintegration in the presenceof steam.

Our invention contemplates alloys of the nature and possessing thecharacteristic properties herein set forth whether or not small amountsof one or more additional elements such as tin, zinc, iron, manganese,magnesium, and (or) silicon are present. The total of the additionalelement or elements should be less than 2% of the alloy and preferablyless than 1%.

Having thus set forth the nature of our in- I vention, what we claim is:

1. An alloy composed of copper, cadmium, nickel and aluminum in amountssubstantially within the following ranges:

Percent Copper 62.0 to 99.77 Cadmium 0.01 to 3.0 Nickel 0.10 to 30.0Aluminum 0.10 to 9.0

2. An alloy composed of copper, cadmium, nickel and aluminum in amountssubstantially Within the following ranges:

Percent Copper 75.0 to 99.73 Cadmium 0.05 to 2.0 Nickel 0.11 to 20.0Aluminum 0.11 to 3.0

3. An alloy comprising approximately 1% cadmium, 5% nickel, 1% to 5%aluminum, and balance copper.

4. An alloy comprising approximately 83.25% copper, 0.75% cadmium, 15%nickel and 1% aluminum.

5. An alloy comprising aproximately 78.5% copper, 0.5% cadmium, 20%nickel and 1% aluminum.

6. A copper base alloy characterized by being capable of hot and coldworking comprising approximately 0.05% to 2.5% cadmium, 0.1% to 30%nickel, 0.1% to 3% aluminum and balance copper wherein the cadmiumcontent is gradually reduced from 2.5% tr! 0.05% as the nickel contentis increased from 0.1% to 30% and as the aluminum content is increasedfrom 0.1% to 3%.

7. A heat treatable copper base alloy capable of being hardened byheating at temperatures from approximately 300 C. to 550 C., comprisingessentially copper, cadmium, nickel and aluminum in amountssubstantially within the following ranges:

Percent Copper 75.0 to 96.7 Cadmium 0.05 to 2.0 Nickel 3.0 to 20.0Aluminum 0.5 to 2.0

8. A heat treatable copper base alloy characterized by being capable ofbeing hardened by heating at temperatures from approximately 300 C. to550 C., composed of 0.11 percent to 2.0 percent cadmium, from 3.0percent to 30.0 percent nickel, from 0.5 percent to 4.0 percentaluminum, and the balance substantially copper.

9. A heat treatable copper base alloy which is characterized by beingcapable of being hardened by heating from approximately 300 C. to 550C., comprising approximately 3% to 30% nickel and 1% to 9% aluminum,0.01% to 2.5% cadmium and balance substantially copper and in which thenickel content exceeds that of the aluminum content by a ratio of about3 to 1.

10. A heat treatable, corrosion resistant copper-cadmium-nickel-aluminumalloy character ized by being capable of being hardened at temperaturesfrom approximately 300 C. to 550 C., in which the nickel content exceedsthe aluminum content, the nickel being at least 3% and not more than30%, the aluminum at least 0.5% and not more than 5%, the cadmium from0.01% to 2.5%, and the balance copper.

11. An alloy characterized by being capable of being hardened by heatingfrom approximately 300 C. to 500 C. and resistant to corrosion,comprising essential amounts of copper, cadmium,

nickel and aluminum substantially within the following ranges:

12. An alloy comprising approximately 0.01%

to 1.5% cadmium, 0.5% to 4% aluminum, 3% to 30% nickel, and balancecopper.

13. A heat hardenable copper-nickel-alumihum-cadmium alloy characterizedby having hardness and other desirable mechanical properties produced byheating said alloy to a temperature of from 700 C. to 900 C. followed byquenching and age hardening by prolonged heating at temperatures in therange approximately from about 300 C. to about 550 C., wherein thenickel content exceeds the aluminum content, the nickel being at least3% and not more than 30%, the aluminum at least 0.5% and not more than5%, the cadmium from 0.05% to 2.5% and the balance copper.

14. A heat hardenable copper-nickel-aluminum-cadmlum alloy characterizedby having hardness and other desirable mechanical properties produced byheating said alloy to a temperature of from 700 C. to 900 C. followed byquenching, cold working, and/or forming and age hardening by prolongedheating at temperatures in the range approximately from about 300 C. toabout 550 C., wherein the nickel content exceeds the aluminum content,the nickel being at le'ast 3% and not more than 30%, the aluminum atleast 0.5% and not more than 5%, the cadmium from 0.05% to 2.5% and thebalance copper.

15. In the heat treatment of the copper-cadmium-nickel-aluminum alloyscontaining from about 0.05% to 2.5% cadmium, from about 3.0% to 30%nickel, from about 0.5% to 5.0% aluminum, with the remainder copper, thesteps which comprise heating such an alloy at temperatures above atransition point, whichlies in the neighborhood of 700 C., but below itsmelt ing point, quenching and age hardening by prolonged heating attemperatures in the range approximately from about 300 C. to about 550C.

16. In the heat treatment of the copper-cadmium-nickel-aluminum alloyscontaining from about 0.05% to 2.5% cadmium, from about 3.0% to 30%nickel, from about 0.5% to 5.0% aluminum, with the remainder copper, thesteps which comprise heating such an alloy at temperatures above atransition point, which lies in the neighborhood of 700 C., but belowits melting point, quenching, cold working, and/or forming and agehardening by prolonged heating at temperatures in the rangeapproximately from about 300 C. to about 550 C.

17. An alloy comprising 62% to 97.77% copper, 0.1% to 30% nickel, 0.01%to 9% aluminum, and sumcient cadmium within the range of 0.01% to 3% toimpart to the alloy materially increased resistance to corrosion insteam and in air at temperatures above normal over the same alloywithout the cadmium.

CHARLES H. DAVIS. ELMER L. MUNSON.

